LOW-ENERGY AR ION-INDUCED AND CHLORINE ION ETCHING OF SILICON

A nearly monoenergetic beam of argon and chlorine ions with kinetic en ergy from 40 to 900 eV and intensity up to 30 mu A/cm(2) is used to st udy the etching of Si. The etch rate and ion current density at the su rface are simultaneously measured to obtain the etch yield. The ratio of atomic chlorine (Cl+) to molecular chlorine (Cl-2(+)) ions striking the surface is measured by a quadrupole mass spectrometer. In the abs ence of any chlorine, the Ar ion sputtering of silicon at 120 eV is ab out 0.05 silicon atoms removed per ion and monotonically increases to 1 silicon atom per ion at 800 eV. The Ar+-induced etch yield increases by about an order of magnitude when the surface is simultaneously exp osed to a neutral molecular chlorine flux sufficient to produce satura tion coverages from the effusive doser. An etch yield of 0.13 silicon atoms removed per incident Ar ion is measured at an Ar+ energy of 50 e V, which also monotonically increases to 4 silicon atoms removed per i ncident argon ion at 700 eV. The etch yield further increases by appro ximately a factor of 20% as the surface is bombarded with energetic ch lorine ions. The etch yield with energetic chlorine ions increases fro m 0.07 to similar to 5 silicon atoms per incident ion with increasing kinetic energy from 40 to 900 eV. (C) 1996 American Vacuum Society.